U.S. patent application number 15/305220 was filed with the patent office on 2017-02-16 for bearing device, conveying device, inspection device, and machine tool.
This patent application is currently assigned to NSK LTD.. The applicant listed for this patent is NSK LTD.. Invention is credited to Hirohide KONISHI.
Application Number | 20170047811 15/305220 |
Document ID | / |
Family ID | 54332539 |
Filed Date | 2017-02-16 |
United States Patent
Application |
20170047811 |
Kind Code |
A1 |
KONISHI; Hirohide |
February 16, 2017 |
BEARING DEVICE, CONVEYING DEVICE, INSPECTION DEVICE, AND MACHINE
TOOL
Abstract
A bearing includes an inner ring and an outer ring arranged to
face each other with a rolling element interposed therebetween, and
a housing including a housing inner supported by the inner ring and
a rotor flange supported by the outer ring. The rotor flange
includes a flange portion extending toward one end surface side in
an axial direction of the outer ring, and a C-type retaining ring
arranged at the other end surface side in the axial direction of
the outer ring. A push ring formed of a resin material is provided
in a gap between the flange portion and the one end surface in the
axial direction.
Inventors: |
KONISHI; Hirohide;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NSK LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
NSK LTD.
Tokyo
JP
|
Family ID: |
54332539 |
Appl. No.: |
15/305220 |
Filed: |
April 22, 2015 |
PCT Filed: |
April 22, 2015 |
PCT NO: |
PCT/JP2015/062270 |
371 Date: |
October 19, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16C 35/073 20130101;
H02K 7/08 20130101; F16C 33/7833 20130101; F16C 35/067 20130101;
F16C 41/00 20130101; F16C 2380/26 20130101; F16C 35/077 20130101;
F16C 2202/22 20130101; B23Q 7/02 20130101; F16C 19/06 20130101;
F16C 25/08 20130101; G01D 5/20 20130101; F16C 33/768 20130101; H02K
11/21 20160101 |
International
Class: |
H02K 7/08 20060101
H02K007/08; F16C 35/077 20060101 F16C035/077; H02K 11/21 20060101
H02K011/21; B23Q 7/02 20060101 B23Q007/02; G01D 5/20 20060101
G01D005/20; F16C 19/06 20060101 F16C019/06; F16C 41/00 20060101
F16C041/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 23, 2014 |
JP |
2014-089367 |
May 15, 2014 |
JP |
2014-101283 |
Mar 4, 2015 |
JP |
2015-042417 |
Claims
1. A bearing device comprising: a bearing including an inner ring
and an outer ring arranged to face each other with a rolling
element interposed therebetween; and a housing including a first
housing supported by the inner ring and a second housing supported
by the outer ring, wherein at least one of the first housing and
the second housing includes a flange portion extending toward one
end surface side in an axial direction of the bearing, and a
retaining ring arranged at the other end surface side in the axial
direction of the bearing, and a push ring formed of a resin
material is provided in a gap between the flange portion and the
one end surface in the axial direction of the bearing, or a gap
between the retaining ring and the other end surface in the axial
direction of the bearing.
2. The bearing device according to claim 1, wherein the at least
one housing in which the flange portion is formed includes a groove
portion extending in a circumferential direction, and the retaining
ring is mounted in the groove portion.
3. The bearing device according to claim 1, wherein the first
housing and the second housing are each formed into a cylindrical
shape, and the at least one housing in which the flange portion is
formed is seamlessly molded in an extending direction of the
cylinder.
4. The bearing device according to claim 1, wherein the push ring
includes a first contact surface being in contact with the flange
portion or the retaining ring, and a second contact surface being
in contact with the one end surface or the other end surface in the
axial direction of the bearing, and the first contact surface and
the second contact surface are formed at positions shifted in a
radial direction of the push ring.
5. The bearing device according to claim 2, wherein the push ring
is provided in the gap between the flange portion and the one end
surface in the axial direction of the bearing, and a first gap
sealing member formed of a resin material is arranged in at least
one of the gap between the retaining ring and the other end surface
in the axial direction of the bearing, and a gap between the
retaining ring and the groove portion.
6. The bearing device according to claim 5, wherein the first gap
sealing member is a resin film sticking on the retaining ring.
7. The bearing device according to claim 5, wherein the first gap
sealing member is an adhesive including a main agent, and a curing
agent that is mixed with the main agent and cures the main
agent.
8. The bearing device according to claim 7, wherein the retaining
ring is mounted in the groove portion in a state where one of the
main agent and the curing agent is applied on the other end surface
in the axial direction of the bearing and the groove portion, and
the other of the main agent and the curing agent is applied on the
retaining ring.
9. The bearing device according to claim 7, wherein the adhesive is
configured such that the curing agent encapsulated in a
microcapsule is mixed in the main agent, and the curing agent and
the main agent are mixed and cured by the microcapsule being broken
by external force.
10. The bearing device according to claim 1, wherein a second gap
sealing member is arranged in at least one of a gap between the
inner ring and the first housing and a gap between the outer ring
and the second housing.
11. The bearing device according to claim 10, wherein the second
gap sealing member is an adhesive that is cured after being filled
in the gap.
12. The bearing device according to claim 10, wherein the first
housing and the second housing are formed of a magnetic body, and
an electroless nickel-phosphorus plating process is performed on
surfaces of the first housing and the second housing in which the
second gap sealing member is arranged.
13. The bearing device according to claim 1, comprising: a motor
unit including a stator fixed to one of the first housing and the
second housing, and a rotor fixed to the other of the first housing
and the second housing and rotatable with respect to the stator;
and a rotation detector configured to detect a rotational state of
the motor unit, wherein the rotation detector is a single resolver
of an incremental type that detects relative displacement of the
rotor with respect to the stator.
14. The bearing device according to claim 13, wherein the resolver
includes a resolver stator fixed to the first housing, and a
resolver rotor facing the resolver stator with a predetermined
interval and fixed to the second housing, and the resolver rotor is
fixed to the second housing to have a space on a surface at an
opposite side to a facing surface facing the resolver stator.
15. The bearing device according to claim 13, comprising: a power
factor detection unit configured to detect a position where a power
factor becomes 0 when power is supplied to the motor unit; and a
translocation control unit configured to control translocation of
the motor unit according to the position where the power factor
becomes 0, and incremental information output from the
resolver.
16. The bearing device according to claim 13, wherein the motor
unit, the bearing, and the resolver are arranged side by side in an
axial direction of the bearing.
17. A conveying device comprising: the bearing device according to
claim 1, wherein the conveying device is configured to convey an
object to be conveyed by rotation of the first housing or the
second housing.
18. An inspection device comprising: the bearing device according
to claim 1; and an inspection unit configured to individually
inspect an object moved by rotation of the first housing or the
second housing.
19. A machine tool comprising: the bearing device according to
claim 1; and a machining unit configured to individually machine an
object moved by rotation of the first housing or the second
housing.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a National Stage of International
Application No. PCT/JP2015/062270, filed Apr. 22, 2015, claiming
priorities based on Japanese Patent Application Nos. 2014-089367,
filed Apr. 23, 2014, 2014-101283, filed May 15, 2014, 2015-042417,
filed Mar. 4, 2015, the contents of all of which are incorporated
herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a bearing device, and a
conveying device, an inspection device, and a machine tool using
the bearing device.
[0004] 2. Description of the Related Art
[0005] Direct drive motors (bearing devices, hereinafter referred
to as DD motors) that employ a drive system (motor load direct
connection type drive system) to directly transmit rotational force
to a rotating body, and rotate the rotating body in a predetermined
direction with respect to a rotated body are conventionally known.
This kind of DD motor includes a bearing including an inner ring
and an outer ring arranged to face each other with a rolling
element interposed therebetween, a first housing supported by the
inner ring, and a second housing supported by the outer ring, and
rotates the first housing or the second housing as an output shaft
(rotating body). The DD motor detects a rotational state (for
example, a rotational speed, a rotating direction, and a rotation
angle) of the output shaft in a more accurate manner in order to
position the output shaft while rotating the output shaft in a
highly accurate manner. Therefore, the support structure of the
bearing to support the housings is important, and especially,
suppression of movement (thrust play) of the bearing in the axial
direction is required. Conventionally, C-type retaining rings have
been often used to fix the bearing in the axial direction of the
bearing. In this technology, a groove with a diameter slightly
larger than an outer diameter of the bearing is machined in one of
the housings (for example, the second housing) near the bearing,
and a C-type retaining ring is mounted in the groove, so that the
bearing is fixed in the axial direction using force of the
retaining ring expanding outward. However, in this technology,
machining errors of the groove and the like need to be taken into
account in addition to dimensional tolerance of the bearing and the
C-type retaining ring in the axial direction, and complete
suppression of the movement of the bearing in the axial direction
is difficult.
[0006] To realize highly accurate rotation of the motor while
suppressing the movement of the bearing in the axial direction, and
firmly support the load fixed to the output shaft, in a
conventionally proposed structure, the first housing and the second
housing are each divided into two parts at bearing portions in the
axial direction such that the divided housings sandwich the
bearing, and the divided housings are fastened with bolts or the
like (for example, see Prior Art 1).
[0007] Prior Art 1: JP 4636432 B2
[0008] By the way, as a product for industrial application, it is
important to configure the bearing incorporable as easily as
possible, and downsize the bearing. In the conventional technology,
the movement of the bearing in the axial direction can be
suppressed, but the support structure of the bearing is
complicated. Furthermore, in a case where the divided housings are
fastened with bolts, a plurality of bolts (for example, six bolts
or more) is typically provided on a concentric circle with the
bearing. The plurality of bolts needs to be uniformly fastened so
that the housings are uniformly in contact with an end surface of
the bearing in the axial direction. Although it is possible for a
human to tighten the bolts little by little while feeling contact
reaction force against screw holes, it takes long to perform the
work, and it has been difficult to automate the work using a
device.
[0009] The present invention solves the above-described problem,
and an objective is to provide a bearing device that can prevent
movement of a bearing in an axial direction with a simple
configuration, and a conveying device, an inspection device, and a
machine tool that use the bearing device.
SUMMARY OF THE INVENTION
[0010] To solve the above-described problem, a bearing device of
the present invention includes: a bearing including an inner ring
and an outer ring arranged to face each other with a rolling
element interposed therebetween; and a housing including a first
housing supported by the inner ring and a second housing supported
by the outer ring. At least one of the first housing and the second
housing includes a flange portion extending toward one end surface
side in an axial direction of the bearing, and a retaining ring
arranged at the other end surface side in the axial direction of
the bearing, and a push ring formed of a resin material is provided
in a gap between the flange portion and the one end surface in the
axial direction of the bearing, or a gap between the retaining ring
and the other end surface in the axial direction of the
bearing.
[0011] According to this configuration, the push ring formed of a
resin material is provided in the gap between the flange portion
and the one end surface in the axial direction of the bearing, or
the gap between the retaining ring and the other end surface in the
axial direction of the bearing. Therefore, this push ring absorbs
width dimensional tolerance of the retaining ring and the bearing
in the axial direction, so that movement of the bearing in the
axial direction can be prevented with a simple configuration.
[0012] In this configuration, the at least one housing in which the
flange portion is formed may include a groove portion extending in
a circumferential direction, and the retaining ring may be mounted
in the groove portion. According to this configuration, the
retaining ring can be easily attached to the housing, and the
structure to support the bearing can be simplified.
[0013] Furthermore, the first housing and the second housing may be
each formed into a cylindrical shape, and the at least one housing
in which the flange portion is formed may be seamlessly molded in
an extending direction of the cylinder. According to this
configuration, the bearing can be supported without increasing the
size in the axial direction of the one housing in which the flange
portion is formed, which enables a decrease in size of the bearing
device.
[0014] Furthermore, the push ring may include a first contact
surface being in contact with the flange portion or the retaining
ring, and a second contact surface being in contact with the one
end surface or the other end surface in the axial direction of the
bearing, and the first contact surface and the second contact
surface may be formed at positions shifted in a radial direction of
the push ring. According to this configuration, a large distortion
amount (deflection amount) of the push ring can be secured when a
load is applied to the push ring, which allows the push ring to be
effectively deformed.
[0015] Furthermore, the push ring may be provided in the gap
between the flange portion and the one end surface in the axial
direction of the bearing, and a first gap sealing member formed of
a resin material may be arranged in at least one of the gap between
the retaining ring and the other end surface in the axial direction
of the bearing, and a gap between the retaining ring and the groove
portion. According to this configuration, the first gap sealing
member seals a gap caused by waviness or warp of the retaining ring
or the groove portion. Therefore, a decrease in rigidity of the
bearing device can be suppressed.
[0016] Furthermore, the first gap sealing member may be a resin
film sticking on the retaining ring. According to this
configuration, the first gap sealing member can be easily arranged
in the gap between the retaining ring and the other end surface in
the axial direction of the bearing, and the gap between the
retaining ring and the groove portion.
[0017] Furthermore, the first gap sealing member may be an adhesive
including a main agent, and a curing agent that is mixed with the
main agent and cures the main agent. According to this
configuration, the adhesive is cured after the retaining ring is
mounted in the groove portion, so that the gap caused by the
waviness or the warp of the retaining ring or the groove portion
can be easily sealed.
[0018] Furthermore, the retaining ring may be mounted in the groove
portion in a state where one of the main agent and the curing agent
is applied on the other end surface in the axial direction of the
bearing and the groove portion, and the other of the main agent and
the curing agent is applied on the retaining ring. According to
this configuration, premixture of the adhesive is unnecessary.
Therefore, the other end surface in the axial direction of the
bearing and the groove portion can be left in a state of the main
agent or the curing agent being applied, which improves flexibility
in the assembling process of the bearing.
[0019] Furthermore, the adhesive may be configured such that the
curing agent encapsulated in a microcapsule is mixed in the main
agent, and the curing agent and the main agent may be mixed and
cured by the microcapsule being broken by external force. According
to this configuration, for example, the adhesive is applied on the
retaining ring in advance, so that the adhesive can be cured after
the retaining ring is mounted in the groove portion, and then it
becomes easy to handle the adhesive.
[0020] Furthermore, a second gap sealing member may be arranged in
at least one of a gap between the inner ring and the first housing
and a gap between the outer ring and the second housing. According
to this configuration, the second gap sealing member seals the gap,
whereby simplification of machining of the first housing and the
second housing can be achieved, and movement of the bearing in the
radial direction can be suppressed.
[0021] Furthermore, the second gap sealing member may be an
adhesive that is cured after being filled in the gap. According to
this configuration, alignment of the center of the bearing, and the
centers of the first housing and the second housing is realized by
balancing of tension by the adhesive filled in the gap.
[0022] Furthermore, the first housing and the second housing may be
formed of a magnetic body, and an electroless nickel-phosphorus
plating process may be performed on surfaces of the first housing
and the second housing in which the second gap sealing member is
arranged. According to this configuration, aligning force can be
increased compared with one on which no electroless
nickel-phosphorus plating process is performed.
[0023] Furthermore, the bearing device of the present invention may
include: a motor unit including a stator fixed to one of the first
housing and the second housing, and a rotor fixed to the other of
the first housing and the second housing and rotatable with respect
to the stator; and a rotation detector configured to detect a
rotational state of the motor unit. The rotation detector may be a
single resolver of an incremental type, the resolver detecting
relative displacement of the rotor with respect to the stator.
According to this configuration, an increase in height of the
housings in the axial direction can be suppressed, and a decrease
in size of the bearing device can be achieved.
[0024] Furthermore, the bearing device of the present invention may
include: a power factor detection unit configured to detect a
position where a power factor becomes 0 when power is supplied to
the motor unit; and a translocation control unit configured to
control translocation of the motor unit according to the position
where the power factor becomes 0, and incremental information
output from the resolver. According to this configuration, the
rotational state of the motor unit can be accurately detected even
with the configuration in which the single resolver is mounted.
[0025] Furthermore, the resolver may be configured from a resolver
stator fixed to the first housing, and a resolver rotor facing the
resolver stator with a predetermined interval and fixed to the
second housing, and the resolver rotor may be fixed to the second
housing to have a space in a surface opposite to a facing surface
facing the resolver stator. According to this configuration, the
resolver is less affected by the outside, and self-inductance is
stabilized. Therefore, relative displacement of the rotor with
respect to the stator can be more accurately detected.
[0026] Furthermore, the motor unit, the bearing, and the resolver
may be arranged side by side in an axial direction of the bearing.
According to this configuration, it is possible to suppress an
increase in size in the radial direction about the rotation axis,
which allows the installation area (so-called footprint) of the
bearing device to be reduced.
[0027] Furthermore, a conveying device of the present invention
includes the above-described bearing device. The conveying device
is configured to convey an object to be conveyed by rotation of the
first housing or the second housing. According to this
configuration, positional accuracy in conveying the object to be
conveyed can be enhanced, and a decrease in size of the conveying
device can be realized.
[0028] An inspection device of the present invention includes: the
above-described bearing device; and an inspection unit configured
to individually inspect an object moved by rotation of the first
housing or the second housing. According to this configuration,
positional accuracy in moving the object to the inspection unit can
be enhanced, and a decrease in size of the inspection device can be
achieved.
[0029] Furthermore, a machine tool of the present invention
includes: the above-described bearing device; and a machining unit
configured to individually machine an object moved by rotation of
the first housing or the second housing. According to this
configuration, the positional accuracy in moving the object to the
machining unit can be enhanced, and a decrease in size of the
machine tool can be realized.
[0030] According to the present invention, the push ring formed of
a resin material is provided in the gap between the flange portion
and the one end surface in the axial direction of the bearing or
the gap between the retaining ring and the other end surface in the
axial direction of the bearing. Therefore, the push ring absorbs
width dimensional tolerance of the retaining ring and the bearing
in the axial direction, whereby movement of the bearing in the
axial direction can be prevented with a simple configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a cross-sectional view illustrating a
configuration of a direct drive motor according to a first
embodiment.
[0032] FIG. 2 is a block diagram illustrating a configuration to
control a rotation angle position of the direct drive motor.
[0033] FIG. 3 is a partially enlarged cross-sectional view
illustrating a cross-sectional shape of a push ring.
[0034] FIG. 4 is a diagram for explaining a procedure of attaching
a push ring molded with a thermoplastic resin.
[0035] FIG. 5 is a partially enlarged cross-sectional view
illustrating a cross-sectional shape of a push ring according to
another embodiment.
[0036] FIG. 6 is a diagram for explaining a procedure of filling a
thermosetting resin between a flange portion and one end surface in
an axial direction of a bearing.
[0037] FIG. 7 is a partial cross-sectional view illustrating a
support structure of a bearing of a direct drive motor according to
a second embodiment.
[0038] FIG. 8 is a partial cross-sectional view illustrating a
support structure of a bearing of a direct drive motor according to
a third embodiment.
[0039] FIG. 9 is a cross-sectional view illustrating a
configuration of a direct drive motor according to a fourth
embodiment.
[0040] FIG. 10 is a schematic configuration diagram of an
inspection device using the direct drive motor according to the
above-described embodiments.
[0041] FIG. 11 is a schematic configuration diagram of a machine
tool using the direct drive motor according to the above-described
embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0042] Modes (embodiments) for implementing the present invention
will be described in detail with reference to the drawings. The
present invention is not limited by the content described in the
embodiments below. Furthermore, the configuration elements
described below include those easily conceived by a person skilled
in the art, and those substantially the same. Furthermore, the
configuration elements described below can be appropriately
combined, and in a case where there is a plurality of embodiments,
the embodiments can be combined.
First Embodiment
[0043] FIG. 1 is a cross-sectional view illustrating a
configuration of a direct drive motor according to a first
embodiment. A direct drive motor (bearing device, hereinafter
referred to as DD motor) 10 can directly transmit rotational force
to a rotating body without having a reduction mechanism (for
example, a reduction gear and a transmission belt) interposed
therebetween, and can rotate the rotating body in a predetermined
direction.
[0044] The DD motor 10 of the present embodiment is configured as a
so-called outer rotor-type motor. The DD motor 10 includes, as
illustrated in FIG. 1, a housing 7 that includes an annular housing
inner (first housing) 3 fixed to a base 1 and an annular rotor
flange (second housing) 5 arranged outside the housing inner 3.
Furthermore, the DD motor 10 includes a motor unit 9 incorporated
between the housing inner 3 and the rotor flange 5, and rotates the
rotor flange 5 with respect to the housing inner 3, and a bearing
11 that rotatably supports the rotor flange 5 with respect to the
housing inner 3.
[0045] The housing inner 3 and the rotor flange 5 are formed into
substantially cylindrical shapes with different diameters, and
arranged on concentric circles with respect to a rotation axis S.
The rotor flange 5 is seamlessly molded in an extending direction
(in an up and down direction in FIG. 1) of the cylinder. That is,
the rotor flange 5 is configured to be continuous, in a
substantially cylindrical manner, throughout the entire periphery
from a lower end portion to an upper end portion in an axial
direction of the rotation axis S, and various workpieces (not
illustrated) can be attached to the upper end portion. By rotating
the rotor flange 5 by the motor unit 9, the various workpieces can
be rotated in a predetermined direction together with the rotor
flange 5. As described above, the rotor flange 5 performs
rotational motion about the rotation axis S by the operation of the
motor unit 9, and thus functions as an output shaft. Furthermore,
the housing inner 3 is configured to be continuous, in a
substantially cylindrical manner, throughout the entire periphery
from the lower end portion to the bearing 11 in the axial direction
of the rotation axis S, and sandwiches the bearing 11 with an inner
ring holder 29.
[0046] The motor unit 9 is arranged at a lower portion of the
housing 7 (near the base 1). The motor unit 9 includes a stator
(stationary element) 13 fixed to an outer peripheral surface of the
housing inner 3, and a rotor (rotating element) 15 fixed to an
inner peripheral surface of the rotor flange 5 and arranged to face
the stator 13. The stator 13 includes motor cores 17 concentrically
arrayed along a rotating direction of the rotor flange 5 at
predetermined intervals (for example, at equal intervals), and
stator coils 19, wires that are wound in a multiple manner, are
fixed to the respective motor cores 17. Wiring for supplying power
from a control unit 20 (FIG. 2) is connected to the stator 13, and
the power is supplied to the stator coil 19 through the wiring. The
rotor 15 is configured from permanent magnets concentrically
arrayed along the rotating direction of the rotor flange 5 at
predetermined intervals (for example, at equal intervals). When
electricity is supplied to the stator coil 19 through the control
unit 20, rotational force is provided to the rotor flange 5
according to the Flemings' left hand rule, and the rotor flange 5
is rotated in a predetermined direction.
[0047] The bearing 11 is arranged at a position farther from the
base 1 than the motor unit 9 is in the axial direction. The bearing
11 includes an inner ring 21 and an outer ring 23 arranged to face
each other in a relatively rotatable manner, and a plurality of
rolling elements 25 provided between the inner ring 21 and the
outer ring 23 in a rollable manner. It is preferable that one
bearing 11 can sustain both of an axial load and a moment load, and
for example, a four point contact ball bearing, a three point
contact ball bearing, a deep-groove radial bearing, or a cross
roller bearing can be employed. In a case of employing the cross
roller bearing, it is preferable to use a bearing having a
structure in which an inner ring and an outer ring are integrated
with each other, instead of using a bearing having a typical
structure in which an inner ring and an outer ring are separately
provided. The inner ring 21 is sandwiched by the housing inner 3
and the inner ring holder 29, and the outer ring 23 is fixed to the
inner peripheral surface of the rotor flange 5. The support
structure of the bearing 11 will be described below.
[0048] Furthermore, the DD motor 10 is provided with a resolver
(rotation detector) 27 for detecting a rotational state (for
example, a rotational speed, a rotating direction, and a rotation
angle) of the motor unit 9 above the bearing 11 (i.e., at a
position farther from the base 1 than the bearing 11 is in the
axial direction). Accordingly, the various workpieces attached to
the rotor flange 5 can be accurately rotated by a predetermined
angle, and can be accurately positioned at a target position.
Furthermore, the resolver 27 is separated and protected from the
outside world by a disk-like cover 31 provided on an upper portion
of the inner ring holder 29 connected to the housing inner 3.
[0049] In the present embodiment, the DD motor 10 is configured
such that the motor unit 9, the bearing 11, and the resolver 27 are
vertically arranged in the housing 7 in the axial direction (in the
up and down direction in FIG. 1) of the rotation axis S.
Accordingly, in the DD motor 10, it is possible to suppress an
increase in dimensions in a radial direction about the rotation
axis S, which allows an installation area (so-called footprint) of
the housing 7 to be reduced. Meanwhile, in recent years, DD motors
in which not only the installation area of the housing but also a
height dimension in the axial direction is decreased have been
desired. Typically, in a DD motor, two types of resolvers including
an absolute resolver and an incremental resolver for performing
positioning of the motor and feedback of speed control are mounted
as rotation detectors in order to accurately detect the rotational
state of the motor unit. These resolvers are vertically arranged in
the axial direction. The resolvers are positioned so as to be
engaged with an inner diameter side of the housing of the motor,
for example, and are fixed with bolts or the like after a resolver
rotor is fixed. In this configuration, the dimension of the DD
motor in the axial direction is increased to mount these two types
of resolvers.
[0050] To solve this problem, in the present embodiment, the single
resolver 27 is arranged in the housing 7. The resolver 27 is an
incremental resolver that detects a relative displacement of the
rotor 15 with respect to the stator 13. The resolver 27 includes an
annular resolver rotor 33 having an inner periphery that is
eccentric with respect to an axial center of the bearing 11, and a
resolver stator 35 that is arranged to face the resolver rotor 33
with a predetermined interval and that detects reluctance change
between the resolver stator 35 and the resolver rotor 33. The
resolver rotor 33 is integrally attached to a resolver rotor fixing
portion 5a formed on the inner peripheral surface of the rotor
flange 5 with a bolt 33a. Furthermore, the resolver stator 35 is
integrally attached to a resolver stator fixing portion 29a formed
on an outer peripheral surface of the inner ring holder 29 with a
bolt 35a. By making the resolver rotor 33 eccentric to change the
distance between the resolver rotor 33 and the resolver stator 35
in a circumferential direction, reluctance is changed according to
a position of the resolver rotor 33. Therefore, a basic wave
component of the reluctance change has one cycle per rotation of
the rotor flange 5, and thus the resolver 27 outputs a resolver
signal (incremental information) changed according to a rotation
angle position of the rotor flange 5.
[0051] FIG. 2 is a block diagram illustrating a configuration to
control the rotation angle position of the DD motor. The control
unit 20 that controls the operation of the DD motor 10 is connected
to the DD motor 10. This control unit 20 includes a power factor
detection unit 41 that detects a power factor from a resolver
signal detected by the resolver 27, a motor current output from the
motor unit 9, and the like, and also includes a translocation
control unit 43 that controls translocation of the motor unit 9
based on the detected power factor and the resolver signal.
[0052] In the embodiment, the power factor detection unit 41
detects a position of the resolver rotor 33 where the power factor
becomes 0 when power is supplied to the motor unit 9 (stator coil
19), and sets the detected position as a reference position. Then,
the power factor detection unit 41 outputs the reference position
to the translocation control unit 43. The translocation control
unit 43 acquires the resolver signal detected by the resolver 27,
and controls translocation timing of the motor current flowing in
the motor unit 9 based on change of the resolver signal and the
reference position. Accordingly, the absolute resolver is not
necessary in detecting the translocation timing of the motor
current. Therefore, it is not necessary to mount the two types of
rotation detectors including the absolute resolver and the
incremental resolver, unlike the conventional configuration.
Therefore, the single resolver configuration can be employed, and
the height of the DD motor 10 in the axial direction can be
suppressed.
[0053] By the way, the DD motor 10 needs to more accurately detect
the rotational state in order to accurately position and rotate the
rotor flange 5 as the output shaft. Therefore, the support
structure of the bearing 11 that supports the housing inner 3 and
the rotor flange 5 is important, and especially, a structure that
enables easy suppression of the movement (thrust play) of the
bearing 11 in the axial direction has been desired. Next, the
support structure of the bearing 11 will be described.
[0054] An outer ring holding portion 50 is formed throughout the
entire periphery of the inner peripheral surface of the rotor
flange 5, as illustrated in FIG. 1, and a flange portion 51 with a
diameter shorter than an outer diameter of the bearing 11 (outer
ring 23) and protruding inward is formed throughout the entire
periphery of the outer ring holding portion 50 at the resolver 27
side. Furthermore, a groove portion 52 with a diameter longer than
the outer diameter of the bearing 11 (outer ring 23) is formed in
the outer ring holding portion 50 at the motor unit 9 side. The
flange portion 51 extends to one end surface (a resolver 27-side
end surface, or one axial-direction end surface) 23a side in the
axial direction of the outer ring 23. The flange portion 51 is
preferably formed such that an inner peripheral surface 51b of the
flange portion 51 is positioned outside an inner peripheral surface
of the outer ring 23 and is positioned inside a chamfer portion of
the outer ring 23. According to this structure, the flange portion
51 can reliably support the outer ring 23 of the bearing 11.
[0055] Furthermore, a C-type retaining ring (retaining ring) 53
having spring force trying to expand in the radial direction is
mounted in the groove portion 52, and the C-type retaining ring 53
extends to the other end surface (a motor unit 9-side end surface,
or the other axial-direction end surface) 23b side in the axial
direction of the outer ring 23. An outer diameter of the groove
portion 52 is slightly larger than an outermost diameter of the
outer ring 23 of the bearing 11, and even if an allowable load of
the bearing 11 itself is applied to the C-type retaining ring 53,
the C-type retaining ring 53 does not come off. As the retaining
ring, not only the C-type retaining ring but also a spring ring can
be used.
[0056] As described above, the bearing 11 is sandwiched by the
flange portion 51 and the C-type retaining ring 53 respectively
provided in the upper and lower portions (both ends) of the outer
ring holding portion 50 in the axial direction. However, the
bearing 11 and the C-type retaining ring 53 usually have
dimensional tolerance in the axial direction, and considering a
machining error of the groove portion 52 and the like, it is
difficult to support the bearing 11 by the flange portion 51 and
the C-type retaining ring 53 while completely suppressing the
movement (thrust play) of the bearing 11 in the axial direction.
Therefore, in the present configuration, a push ring 55 (FIG. 3)
formed of a polymeric resin material is arranged in a gap between
the one end surface 23a in the axial direction of the outer ring 23
and the flange portion 51. Because the push ring 55 is annually
formed of a polymeric resin material such as a thermoplastic resin
and a thermosetting resin, the push ring 55 can absorb width
dimensional tolerance of the bearing 11 in the axial direction, and
completely prevents the bearing 11 from moving in the axial
direction.
[0057] In a case of providing the push ring 55 made of a
thermoplastic resin in the DD motor 10, like the present
embodiment, it is preferable to use a thermoplastic resin having
heat resistance at 100.degree. C. or more. Furthermore, it is
preferable to use a thermoplastic resin having excellent
characteristics such as compressive yield strength, bend strength,
and a compressive elastic modulus (or a tensile elastic modulus, a
Young's modulus, or the like). As a specific example, a material
called super engineering plastic such as polyether ether ketone
(PEEK), polyether sulfone (PES), and polyphenylene sulfide (PPS) is
preferable in terms of heat resistant temperature and mechanical
properties. Furthermore, in a case where resistance to solvents is
required, a crystalline resin is preferable. However, for the DD
motor 10, either of the crystalline resin or a non-crystalline
resin can be used. Furthermore, in molding the push ring, the
thermoplastic resin, which can be used not only in machining
operation but also in metal molding, is more preferable.
[0058] Furthermore, a distortion amount required for the push ring
55 molded with a thermoplastic resin can be calculated from
variation in thickness of the C-type retaining ring 53, machining
errors of the position and the height of the groove portion 52, the
width dimensional tolerance of the bearing 11 in the axial
direction, and the like. This distortion amount is a distortion
amount in a state where the basic dynamic load rating of the
bearing 11 is applied so that the bearing 11 is not damaged. Here,
the flange portion 51 and the outer ring 23 have nearly the same
diameter dimensions. Therefore, when the push ring 55 has a simple
flat ring shape that has nearly the same diameter dimension as the
outer ring 23, the distortion amount is determined according to a
vertical elastic modulus and the Young's modulus of the resin, and
thus only a small distortion amount can be allowed. Therefore, in
the present embodiment, as illustrated in FIG. 3, the push ring 55
includes a first contact surface 55a that is in contact with a
support surface 51a of the flange portion 51, and a second contact
surface 55b that is in contact with the one end surface 23a in the
axial direction of the outer ring 23. The first contact surface 55a
and second contact surface 55b are formed at positions shifted in
the radial direction of the push ring 55. To be specific, the push
ring 55 has a substantially hexagonal shape in a cross section, and
includes a first inclined surface 55c that is continuous to the
first contact surface 55a and is inclined in a direction away from
the support surface 51a, and a second inclined surface 55d that is
continuous to the second contact surface 55b and is inclined in a
direction away from the one end surface 23a in the axial direction.
Then, the second inclined surface 55d is provided below the first
contact surface 55a in the axial direction, and the first inclined
surface 55c is provided above the second contact surface 55b in the
axial direction. Accordingly, when a load in the axial direction is
applied to the push ring 55, the push ring 55 is distorted using a
gap between the second inclined surface 55d and the one end surface
23a in the axial direction of the outer ring 23, thereby securing a
large distortion amount (deflection amount) of the push ring 55,
and performing effective deformation.
[0059] Once arranged, the push ring 55 has compression
characteristics of being not substantially changed depending on
temperature, a moderate creep property, and fatigue
characteristics, and thus can suppress movement of the bearing 11
in the axial direction in a state of being incorporated in the DD
motor 10. Furthermore, for example, even when an external load is
applied to the rotor flange 5, displacement is small, and thus the
resolver 27 is not erroneously operated. Therefore, even in a
configuration to perform operation control with the single resolver
27 like the present configuration, it is possible to perform highly
accurate rotation control. Furthermore, because the push ring 55 is
molded with a resin material excellent in the compression
characteristics, the displacement returns to the original state
when the external load is removed.
[0060] As described above, in the present embodiment, the rotor
flange 5 includes the flange portion 51 extending toward the one
end surface 23a side in the axial direction of the outer ring 23 of
the bearing 11, and the C-type retaining ring 53 arranged at the
other end surface 23b side in the axial direction of the outer ring
23, and the push ring 55 formed of a resin material is arranged in
the gap between the flange portion 51 and the one end surface 23a
in the axial direction. Therefore, the width dimensional tolerance
of the bearing 11 in the axial direction can be absorbed, and the
movement of the bearing 11 in the axial direction can be completely
prevented with the simple configuration.
[0061] Next, a procedure of attaching the push ring 55 molded with
a thermoplastic resin will be described. FIG. 4 is a
cross-sectional view for explaining a procedure of attaching the
push ring 55. To be specific, as illustrated in FIG. 4, the push
ring 55 is arranged between the flange portion 51 and the bearing
11, and a jig 60 including a main body portion 60A to be fit into
the inner ring 21 of the bearing 11, and a flange 60B to be in
contact with the inner ring 21 in an outer peripheral portion of
the main body portion 60A is attached. Then, a load in a
compression direction (in the A direction in FIG. 4) is applied to
the bearing 11 and the push ring 55 using the jig 60, and during
this time, the C-type retaining ring 53 is mounted in the groove
portion 52. Accordingly, the bearing 11 can be assembled in a state
where no gap exists in the axial direction of the bearing 11. The
load in the compression direction at the time of assembling is
preferably the axial basic dynamic load rating of the bearing 11 or
less, and is set to the axial basic static load rating or less at
most, so that damage on the bearing 11 at the time of assembling
can be prevented.
[0062] In the present embodiment, the push ring 55 having the
substantially hexagonal shape in cross section has been described
as an example of the shape of the push ring 55. However, the shape
of the push ring is not limited to the above example. For example,
as illustrated in FIG. 5, a push ring 155 including a first contact
surface 155a being in contact with the support surface 51a of the
flange portion 51, and second contact surfaces 155b and 155c being
in contact with the one end surface 23a in the axial direction of
the outer ring 23 may be employed. In this push ring 155, the
second contact surfaces 155b and 155c are formed separated from
each other in the radial direction, a cavity portion 155d is
provided between the second contact surfaces 155b and 155c, and the
first contact surface 155a is positioned above the cavity portion
155d in the axial direction. That is, the push ring 155 has a
configuration in which the first contact surface 155a and the two
second contact surfaces 155b and 155c are shifted in the radial
direction. Even with this shape, the push ring 155 can secure a
large distortion amount (deflection amount) of the push ring 155 by
being distorted using the cavity portion 155d, which allows the
push ring 155 to be effectively deformed.
[0063] Furthermore, in the above-described embodiment, the push
ring 55 formed of the thermoplastic resin has been described.
However, for example, the push ring may be formed by filling a
thermosetting resin between the flange portion 51 and the one end
surface 23a in the axial direction of the bearing 11 (outer ring
23). As the thermosetting resin to be used, a two-liquid mixing
type epoxy resin-based adhesive is the most preferable. This
adhesive has the following advantages. Firstly, because the
adhesive requires a long curing time, it is easy to secure time to
fill the thermosetting resin while a compressive load is applied
around the bearing 11. Secondly, while curing progresses at normal
temperature, it is possible to accelerate the curing progress by
raising the temperature a little such as to 60.degree. C. Thirdly,
the adhesive is less affected by variation of cure conditions due
to a work environment compared to a two-liquid type that reacts
with humidity in the air or the like. Furthermore, because grease
is filled in the bearing 11, a type that causes a curing reaction
within a use temperature range of the bearing 11 is preferable. The
epoxy resin-based adhesive is also characterized in that it has the
least variation in mechanical strength (for example, tensile shear
strength) even if temperature rises. A total of dimension variation
of the bearing 11 or the C-type retaining ring 53 is about 0.06 mm,
typically 0.2 mm or less, which provides appropriate conditions to
cure the epoxy resin. Furthermore, the epoxy resin-based adhesive
is characterized in that compressive strength is higher than shear
strength or peel strength, and thus the epoxy resin-based adhesive
is preferable as a material to be filled in the gap.
[0064] FIG. 6 is a diagram for explaining a procedure of filling
the thermosetting resin between the flange portion 51 and the one
end surface 23a in the axial direction of the bearing 11 (outer
ring 23). In the case of using the thermosetting resin, the
compressive load is applied in a direction of filling the gap
between the C-type retaining ring 53 and the bearing 11 in the
axial direction (direction of B in FIG. 6), using a pushing jig 70
illustrated in FIG. 6 in a state where the bearing 11 is
incorporated in the flange portion 51 and the C-type retaining ring
53 is also incorporated. Then, in a state where the compressive
load is being applied, the thermosetting resin that has been mixed
and in which the chemical reaction has started but curing has not
started yet (not cured) is filled into the gap using a small tube
71 to mold a push ring 255. In consideration of the compressive
strength, temperature contraction, and a creep property of the
resin among mechanical characteristics of the thermosetting resin
to be filled, the compressive load is preferably set to a value by
which the mechanical characteristics of the push ring 255 do not
pose a problem when using the motor. Furthermore, as illustrated in
FIG. 6, the thermosetting resin may be filled in a state where the
bearing 11 is pushed into the C-type retaining ring 53 side using
the pushing jig 70. Furthermore, as another method, a tap is
provided to the flange portion 51, and the pushing may be performed
by a tap screw. Alternately, the thermosetting resin is applied on
the flange portion 51 in advance, the C-type retaining ring 53 is
installed such that the gap between the C-type retaining ring 53
and the bearing 11 can be adjusted, and then the thermosetting
resin may be interposed therebetween.
Second Embodiment
[0065] By the way, the housing 7 (the housing inner 3 and the rotor
flange 5) that supports the bearing 11 is manufactured by a
machining operation such as a lathe. Therefore, unevenness called
surface roughness is caused on a machining surface as a trace of
cutting by a rotating edged tool (for example, JIS B0601 described
as Ra1.6, Ra3.2, Ra6.3, or the like,). Furthermore, waviness (wave)
is caused in a circumferential direction on an end surface in the
axial direction of the machining surface. This waviness is caused
by propagation of deformation due to a chuck at the time of lathe
machining, and can be removed (finishing as a smooth surface) by
increasing machining processes of a lathe or adding grinding
processes. However, there remains a problem that machining
operation processes increase and become complicated.
[0066] Meanwhile, the C-type retaining ring 53 is manufactured such
that a material such as hard steel wire or stainless steel is
pressed or rolled. Burr, flash, or sagging is caused on an end
surface of the C-type retaining ring 53 at the time of
manufacturing, and the C-type retaining ring 53 as a whole is
warped like a potato chip. On the other hand, as the material for
the bearing 11, metal having high mechanical strength and hardness
such as SUJ2 is employed, and the grinding process is always
performed on the end surfaces in the axial direction of the inner
ring 21 and the outer ring 23 of the bearing 11, and thus the
bearing 11 has smooth and beautiful surfaces.
[0067] The bearing device like the DD motor 10 is usually conveyed
with various loads being mounted, and is used with another load
being applied to the various loads. That is, various external loads
are applied, and thus the DD motor 10 is required to be less likely
to be displaced according to the external loads. Typically, it is
preferable that the DD motor 10 has high rigidity. However, if the
housing 7 has the trace of the edged tool or the waviness, and the
C-type retaining ring 53 has the warp such as the burr or the
flash, the components are deformed in a direction in which the
waviness or the warp on the end surfaces of the components (the
housing 7 or the C-type retaining ring 53) is crushed (flattened)
when the external load is applied thereto, even if the bearing 11
is not moved in the axial direction. Therefore, there is a problem
of a decrease in rigidity of the DD motor 10. Furthermore, due to
the waviness or the warp, contact areas of the end surfaces in the
axial direction of the components are reduced, and thus even
fretting wear may be possibly caused in the end surfaces in the
axial direction of these types of components due to drive vibration
or the like.
[0068] In the DD motor 10 of the first embodiment, the rotor flange
5 includes the flange portion 51 extending toward the one end
surface 23a side in the axial direction of the outer ring 23 of the
bearing 11, and the C-type retaining ring 53 arranged at the other
end surface 23b side in the axial direction of the outer ring 23,
and the push ring 55 formed of a resin material is arranged in the
gap between the flange portion 51 and the one end surface 23a in
the axial direction of the outer ring 23. According to this
configuration, the push ring 55 absorbs the width dimensional
tolerance of the C-type retaining ring 53 and the bearing 11 in the
axial direction, thereby preventing the movement of the bearing 11
in the axial direction with a simple configuration, and suppressing
the influence of the waviness and the warp described above.
[0069] Meanwhile, in the configuration of the DD motor 10 of the
first embodiment, the waviness or the warp may be deformed between
the C-type retaining ring 53 and the other end surface 23b in the
axial direction of the outer ring 23 (bearing 11), and between the
C-type retaining ring 53 and the end surface in the axial direction
of the groove portion 52. Therefore, a problem of a decrease in
rigidity of the DD motor 10 has been expected. As a noticeable
example, there may be a problem that the rigidity of the DD motor
10 (displacement caused by application of the load) differs, due to
the deformation of the waviness or the warp, between a case where a
load in a pure axial direction is applied in a direction in which
the push ring 55 is crushed, and a case where a load in a pure
axial direction is applied in a direction in which the C-type
retaining ring 53 is crushed. A second embodiment is intended to
prevent movement of a bearing 11 in an axial direction, and
suppress a decrease in rigidity of a DD motor 10 due to warp caused
in a C-type retaining ring 53 or waviness caused in a groove
portion 52 to which the C-type retaining ring 53 is mounted.
[0070] FIG. 7 is a partial cross-sectional view illustrating a
support structure of a bearing of a direct drive motor according to
the second embodiment. In the second embodiment, different portions
from the first embodiment will be described to avoid overlapping
description, and portions having similar configurations to those of
the first embodiment are denoted with the same reference signs, and
description thereof is omitted.
[0071] As illustrated in FIG. 7, in a DD motor 10A, first gap
sealing members 65 made of a polymeric resin material are
respectively arranged in a gap between one end surface 53a in an
axial direction of a C-type retaining ring 53 and the other end
surface 23b in an axial direction of an outer ring 23 (bearing 11),
a gap between the one end surface 53a in the axial direction of the
C-type retaining ring 53 and one end surface 52a in an axial
direction of a groove portion 52, and a gap between the other end
surface 53b in the axial direction of the C-type retaining ring 53
and the other end surface 52b in the axial direction of the groove
portion 52. The first gap sealing member 65 is formed of a
polymeric resin material such as a thermoplastic resin and a
thermosetting resin, and has a function to fill (seal) a gap caused
by waviness or warp of the C-type retaining ring 53 or the groove
portion 52.
[0072] The first gap sealing member 65 is preferably a resin
material having excellent mechanical strength characteristics such
as compressive yield strength, bend strength, and compressive
elastic modulus (or a tensile elastic modulus or a Young's
modulus), similarly to the push ring 55. This first gap sealing
member 65 is arranged in the gap between the one end surface 53a in
the axial direction of the C-type retaining ring 53 and the other
end surface 23b in the axial direction of the outer ring 23
(bearing 11), the gap between the one end surface 53a in the axial
direction of the C-type retaining ring 53 and the one end surface
52a in the axial direction of the groove portion 52, and the gap
between the other end surface 53b in the axial direction of the
C-type retaining ring 53 and the other end surface 52b in the axial
direction of the groove portion 52. Accordingly, the first gap
sealing member 65 fills (seals) the gap caused by the waviness or
the warp of the C-type retaining ring 53 or the groove portion 52.
Therefore, a decrease in rigidity of the DD motor 10 can be
suppressed. Furthermore, occurrence of fretting wear can be
prevented.
[0073] The gap caused by the waviness or the warp of the C-type
retaining ring 53 or the groove portion 52 is very small in
dimension (for example, 75 .mu.m), and thus a paste-like or
film-like resin can be selected. To be specific, it is preferable
to use polyamide-imide (PAI) formed in a film manner as the
thermoplastic resin, or an epoxy resin-based adhesive or an acrylic
resin-based adhesive as the thermosetting resin.
[0074] As a procedure of installing the first gap sealing member
65, in a case of using the polyamide-imide (PAI) formed in a film
manner, polyamide-imide films (resin films) are respectively stuck
on the one end surface 53a and the other end surface 53b in the
axial direction of the C-type retaining ring 53 in advance, and
then the C-type retaining ring 53 is mounted in the groove portion
52. In this configuration, the first gap sealing member 65 can be
easily arranged.
[0075] Furthermore, in a case of using the two-liquid mixing type
epoxy resin-based adhesive, the main agent and the curing agent of
the epoxy resin-based adhesive are mixed, and the mixed liquid is
applied on the other end surface 23b in the axial direction of the
outer ring 23 (bearing 11), the one end surface 53a and the other
end surface 53b in the axial direction of the C-type retaining ring
53, and the one end surface 52a and the other end surface 52b in
the axial direction of the groove portion 52 in advance, and then
the C-type retaining ring 53 is mounted in the groove portion 52.
In this configuration, the adhesive is cured after the C-type
retaining ring 53 is mounted, whereby the gap caused by the
waviness or the warp can be easily filled.
[0076] Furthermore, as the adhesive made of a thermosetting resin,
an acrylic resin-based adhesive can be used. The acrylic
resin-based adhesive has two liquids but the two liquids do not
need to be mixed. The adherend is promptly cured only by applying a
main agent and a curing agent (promotor) on one surface of each
adherend, and crimping them. The acrylic resin-based adhesive has a
short set time (fixing time), which is about five minutes, and
tensile shear strength is 19.6 MPa (200 kgf/cm.sup.2) and T-type
peel strength is 3.9 kN/m (10 kgf/25 mm) or more. This exhibits
performance as good as that of the epoxy resin-based adhesive.
Furthermore, the acrylic resin-based adhesive is excellent in oil
surface adhesiveness, shock resistance, and durability.
[0077] Therefore, in the case of using the acrylic resin-based
adhesive, for example, the main agent is applied on the other end
surface 23b in the axial direction of the outer ring 23 (bearing
11), and the one end surface 52a and the other end surface 52b in
the axial direction of the groove portion 52, and the curing agent
(promotor) is applied on the one end surface 53a and the other end
surface 53b in the axial direction of the C-type retaining ring 53.
Then, the C-type retaining ring 53 is mounted in the groove portion
52. Furthermore, a configuration in which the main agent is applied
on the one end surface 53a and the other end surface 53b in the
axial direction of the C-type retaining ring 53 may be employed.
According to this configuration, the adhesive is cured by pressure
applied to the end surfaces of the C-type retaining ring 53 after
the C-type retaining ring 53 is mounted, and can easily fill the
gap caused by the waviness or the warp. Furthermore, in this
configuration, premixture of the adhesive is unnecessary.
Therefore, the other end surface 23b in the axial direction of the
outer ring 23 (bearing 11), and the one end surface 52a and the
other end surface 52b in the axial direction of the groove portion
52 can be left in a state of the main agent or the curing agent
being applied, which improves flexibility in the assembling process
of the bearing 11.
[0078] Furthermore, the acrylic resin-based adhesive configured
such that microcapsules encapsulating the curing agent are mixed in
the main agent may be used. The adhesive of this type is applied on
the other end surface 23b in the axial direction of the outer ring
23 (bearing 11) and the one end surface 52a and the other end
surface 52b in the axial direction of the groove portion 52 in
advance, and then the C-type retaining ring 53 is mounted in the
groove portion 52. Furthermore, a configuration in which the
adhesive is applied on the one end surface 53a and the other end
surface 53b in the axial direction of the C-type retaining ring 53
may be employed. In this configuration, the microcapsules are
broken by pressure caused when the C-type retaining ring 53 is
mounted, and the encapsulated curing agent and the main agent are
mixed and cured. Therefore, it is possible to cure the adhesive
after the C-type retaining ring 53 is mounted by applying the
adhesive on the one end surface 53a and the other end surface 53b
in the axial direction of the C-type retaining ring 53 in advance,
for example, and then it becomes easy to handle the adhesive.
Third Embodiment
[0079] As described above, the housing 7 (the housing inner 3 and
the rotor flange 5) that supports the bearing 11 is manufactured by
a machining operation such as using a lathe. To be specific, one
side of the material (base material) is held with three to four
claws of a mounting tool called a chuck, and the material is cut by
a cutting tool (edged tool) being pressed against the opposite side
of the material while rotating the material. In this way, the outer
peripheral surfaces and the inner peripheral surfaces of the
cylindrical housing inner 3 and the rotor flange 5 are
machined.
[0080] Since the housing inner 3 and the rotor flange 5 support the
inner ring 21 and the outer ring 23 of the bearing 11, enhancement
of the roundness is important in machining the outer peripheral
surface of the housing inner 3 and the inner peripheral surface of
the rotor flange 5. Meanwhile, in the machining operation by a
lathe, an end portion of the material is held with the chuck claws
while the direction of the material is changed several times, and
the material is cut by using various types of edged tools such as a
tool for rough cutting and a tool for finishing cutting. In this
case, if a small contaminant enters between the material and the
claws, or if the held position of the material is imbalanced,
coaxiality of the material becomes poor, affecting the shape of the
cut portion. Furthermore, the material may be warped by being held
with the chuck claws, and this warp has a lasting influence on not
only the held portion, but also on the shape of the cut portion at
an opposite side to the held side. Therefore, it requires a mature
technique to determine the held portion.
[0081] To eliminate the warp of the material due to the chuck
claws, usually, the cutting process is divided into several times
and repeatedly performed to gradually enhance the roundness of the
shape, and make dimension accuracy closer to a design value.
Furthermore, in many cases, not only the cutting with the edged
tool but also machining with a grinding stone is performed. As
described above, in the machining of the housing 7 (the housing
inner 3 and the rotor flange 5) in which the bearing 11 is
incorporated, there is a problem of requiring many processes and
labors in order to enhance the roundness, and eliminate (completely
remove) the gap between the outer peripheral surface of the housing
inner 3 and the inner peripheral surface of the bearing 11 (inner
ring 21) and the gap between the inner peripheral surface of the
rotor flange 5 and the outer peripheral surface of the bearing 11
(outer ring 23).
[0082] Meanwhile, in a case where the roundness of the outer
peripheral surface of the housing inner 3 and the roundness of the
inner peripheral surface of the rotor flange 5 are not sufficient,
that is, in a case where the shape of the outer peripheral surface
or that of the inner peripheral surface is a triangular shape
(polygonal shape) or an elliptical shape, gaps (cavities) are
caused between the outer peripheral surface of the housing inner 3
and the inner peripheral surface of the bearing 11 (inner ring 21),
and between the inner peripheral surface of the rotor flange 5 and
the outer peripheral surface of the bearing 11 (outer ring 23).
[0083] In this state, when a combined load (moment load) is applied
to the DD motor 10, the bearing 11 and the housing 7 (the housing
inner 3 and the rotor flange 5) are moved by an amount
corresponding to the above-described gap due to a load component of
the bearing 11 in the radial direction. As a result, highly
accurate rotation in the DD motor 10 cannot be expected, and in
addition, the movement leads to erroneous detection in the resolver
27. Furthermore, in a case where the outer peripheral surface of
the housing inner 3 or the inner peripheral surface of the rotor
flange 5 is warped, the warped portion and the bearing 11 are
partially in a metal contact state. Therefore, fretting wear occurs
and damages the bearing 11, and variation in rigidity of the DD
motor 10 may be caused depending on a load direction.
[0084] In the DD motor 10 of the first embodiment, the rotor flange
5 includes the flange portion 51 extending toward the one end
surface 23a side in the axial direction of the outer ring 23 of the
bearing 11, and the C-type retaining ring 53 arranged at the other
end surface 23b side in the axial direction of the outer ring 23,
and the push ring 55 formed of a resin material is arranged in the
gap between the flange portion 51 and the one end surface 23a in
the axial direction of the outer ring 23. According to this
configuration, the push ring 55 absorbs the width dimensional
tolerance of the C-type retaining ring 53 and the bearing 11 in the
axial direction, whereby the movement of the bearing 11 in the
axial direction can be prevented with a simple configuration.
[0085] However, in the above configuration, in a case where the gap
in the radial direction is caused between the bearing 11 and the
housing 7 (the housing inner 3 and the rotor flange 5), a movement
amount of the bearing 11 in the radial direction becomes large, and
loads in a shearing direction and in a peeling direction are
applied to the push ring 55. The push ring 55 is formed of a
polymeric resin material. Therefore, if an extra load other than
the compressive load in the axial direction is applied to the push
ring 55, an allowable load of the DD motor 10 is limited, and
further, resin materials that can be selected are also limited.
[0086] A third embodiment is intended to achieve simplification of
machining of a housing 7, and suppress movement of a bearing 11 in
a radial direction.
[0087] FIG. 8 is a partial cross-sectional view illustrating a
support structure of a bearing of a direct drive motor according to
the third embodiment. In the third embodiment, different portions
from the first embodiment will be described to avoid overlapping
description, and portions having similar configurations to the
first embodiment are denoted with the same reference signs and
description thereof is omitted. Furthermore, the configuration of
the C-type retaining ring 53 of the second embodiment may be
combined with that of the third embodiment.
[0088] As illustrated in FIG. 8, a DD motor 10B includes a housing
7 constituted of a housing inner 3 and a rotor flange 5. In the
third embodiment, an outer peripheral surface 30a of an inner ring
holding portion 30 of the housing inner 3 and an inner peripheral
surface 50a of the outer ring holding portion 50 of the rotor
flange 5 are formed by reducing machining processes and labors.
Accordingly, the roundness of the outer peripheral surface 30a of
the inner ring holding portion 30 and the roundness of the inner
peripheral surface 50a of the outer ring holding portion 50 are not
sufficient. Furthermore, gaps are respectively provided between the
outer peripheral surface 30a of the inner ring holding portion 30
and an inner peripheral surface 21c of an inner ring 21 of a
bearing 11 and between the inner peripheral surface 50a of the
outer ring holding portion 50 and an outer peripheral surface 23c
of an outer ring 23 of the bearing 11. Each of diametral clearance
gaps is roughly set to about 17 .mu.m to 23 .mu.m, and set to about
34 .mu.m to 46 .mu.m at a maximum (a radial clearance gap is half
of the diametral clearance gap, and an absolute value of the gap is
half of the radial clearance gap), as an effective value in a case
of manufacturing a columnar component in two lathe turning
processes. In a case of fitting the bearing 11 into the housing
inner 3 and the rotor flange 5 by "interference fitting",
distortion of the outer peripheral surface 30a of the inner ring
holding portion 30 and the inner peripheral surface 50a of the
outer ring holding portion 50 due to lathe machining is transmitted
to a bearing raceway surface, which hinders accurate rotation of
the bearing 11. As a result, it may become difficult to structure a
highly accurate bearing device. Therefore, in the present
embodiment, the gaps are respectively provided between the outer
peripheral surface 30a of the inner ring holding portion 30 and the
inner peripheral surface 21c of the inner ring 21 of the bearing
11, and between the inner peripheral surface 50a of the outer ring
holding portion 50 and the outer peripheral surface 23c of the
outer ring 23 of the bearing 11, which enables the accurate
rotation of the bearing 11.
[0089] Therefore, as illustrated in FIG. 8, in the DD motor 10B,
second gap sealing members 66 made of a polymeric resin material
are respectively arranged in the gap between the inner peripheral
surface 50a of the outer ring holding portion 50 (rotor flange 5)
and the outer peripheral surface 23c of the outer ring 23 (bearing
11), and the gap between the outer peripheral surface 30a of the
inner ring holding portion 30 (housing inner 3) and the inner
peripheral surface 21c of the inner ring 21 (bearing 11). This
second gap sealing member 66 is an adhesive made of a thermosetting
resin, and has a function to fill (seal) the gaps caused at the
time of machining.
[0090] When adhesives made of thermosetting resins are classified
according to characteristics exhibited at high temperature, there
are structural adhesives and non-structural adhesives. It is more
preferable to use a structural adhesive. Furthermore, a modified
structural adhesive or a combined thermosetting resin adhesive, in
which desired characteristics have been obtained by adjusting
temperature conditions, can also be used. These types of adhesives
are excellent in: (1) application workability (fluidity); (2)
surface (interfacial) tension (wettability); and (3) cohesive force
of the polymeric material (intermolecular force and bonding
strength) and mechanical physical properties after being cured.
[0091] To provide the adhesive in the gaps, the adhesive needs to
be applied on the inner and outer peripheral surfaces of the
bearing 11 and the housing 7 (the housing inner 3 and the rotor
flange 5). Because the bearing 11 is incorporated into the housing
7 after the adhesive is applied, it requires a certain amount of
time from the application of the adhesive to the incorporation. The
adhesive made of a thermosetting resin has viscosity of 80 Pas
before curing (a mixture of the main agent and the curing agent),
or about half of 80 Pas. Therefore, a work to apply the adhesive to
the inner and outer peripheral surfaces of the bearing 11 and the
housing 7 (the housing inner 3 and the rotor flange 5) can be
easily performed.
[0092] Next, the surface (interfacial) tension (wettability) is
force to attract the polymer material to the inner and outer
peripheral surfaces of the bearing 11 and the housing 7. Both the
bearing 11 and the housing 7 (the housing inner 3 and the rotor
flange 5) are made of metal. When the adhesive is applied on metal
surfaces thereof, the surface (interfacial) tension works, and then
distortion and waviness occur. Accordingly, tension is balanced in
every place of the gaps between the bearing 11 and the housing 7
(the housing inner 3 and the rotor flange 5). As a result, an
action to adjust (align) a rotation center of the bearing 11 and an
axial center of the housing 7 (the housing inner 3 and the rotor
flange 5) is caused. To be specific, even if the gap between the
outer peripheral surface 23c of the outer ring 23 of the bearing 11
and the inner peripheral surface 50a of the outer ring holding
portion 50 of the rotor flange 5 is about 45 .mu.m before filling
of the adhesive, rotary deflection of the rotor flange 5 (output
shaft) in the radial direction is adjusted to 30 .mu.m or less by
the aligning action that occurs when the adhesive is filled into
the gap.
[0093] In the third embodiment, the C-type retaining ring 53 and
the push ring 55 are arranged respectively on the end surface in
the axial direction of the bearing 11. Although the C-type
retaining ring 53 and the push ring 55 restrain the movement of the
bearing 11 in the axial direction, restraining force (contact force
and contact frictional force) of the bearing 11 in the radial
direction is low. Therefore, the C-type retaining ring 53 and the
push ring 55 do not impede the aligning action by the adhesive.
[0094] Furthermore, it is possible but complicated to measure force
(aligning force) itself acting on the aligning action described
above. Therefore, a value of the adhesive interface strength that
is measured when the bearing 11 is pulled out of the housing 7 (the
housing inner 3 and the rotor flange 5) after the adhesive is cured
provides an indication of the aligning force. As the measured value
of the adhesive interface strength, about 12 N/mm.sup.2 is an ideal
value. However, even if the value is 3.7 N/mm.sup.2 or more, the
effect of the aligning action is exhibited.
[0095] Furthermore, the aligning force tends to be influenced by a
surface state or a type of surface treatment of the inner
peripheral surface 50a of the outer ring holding portion 50 and the
outer peripheral surface 30a of the inner ring holding portion 30,
to which the adhesive is applied. In the third embodiment, films 67
formed by electroless nickel-phosphorus plating are respectively
provided on the inner peripheral surface 50a of the outer ring
holding portion 50 and the outer peripheral surface 30a of the
inner ring holding portion 30. In a case where the housing inner 3
and the rotor flange 5 are formed of iron (magnetic body), the
configuration in which the films 67 are formed by the electroless
nickel-phosphorus plating has more activated surfaces compared with
a configuration where an iron surface is exposed on the inner
peripheral surface 50a and the outer peripheral surface 30a, or a
configuration where a film formed by low-temperature chrome plating
is provided on the inner peripheral surface 50a and the outer
peripheral surface 30a. Therefore, it has been found that the
present configuration exhibits high aligning force. Furthermore, in
an electroless nickel-phosphorus plating process, the adhesive
property is high when the phosphorus concentration is high, and the
aligning force can be increased. Furthermore, by performing the
electroless nickel-phosphorus plating process, the corrosion
resistance is enhanced, and the rotation accuracy of the DD motor
10B can be maintained high over time.
[0096] Furthermore, in the electroless nickel-phosphorus plating
process, the film 67 becomes non-crystalline and non-magnetic when
the phosphorus concentration is high. Therefore, in the
configuration where the resolver 27 is provided in the housing 7
(the housing inner 3 and the rotor flange 5), an influence of
magnetic force on the resolver 27 can be suppressed, and the
rotation accuracy of the DD motor 10B can be enhanced from the
electric perspective.
[0097] Finally, the cohesive force and mechanical physical
properties that are exhibited after curing of the polymeric
material are characteristics that influence the mechanical rigidity
when the DD motor 10B is actually used, and are characteristics
that influence reliability of a structure including the C-type
retaining ring 53 and the push ring 55. The adhesive made of a
thermosetting resin (to be specific, the epoxy resin-based
adhesive) has less occurrence of internal distortion after curing,
and the mechanical strength of the resin material itself is high.
Therefore, the adhesive can sufficiently satisfy the mechanical
rigidity of the DD motor 10B. Furthermore, interfacial failure
strength and cohesive failure strength can be arbitrarily adjusted
according to a mixture of the resin materials of the adhesive. It
is preferable to determine the resin mixture of the adhesive to
satisfy the aligning force and the mechanical rigidity in a
well-balanced manner. Specific examples include a room temperature
curing-type epoxy resin adhesive and a one-liquid epoxy adhesive.
Because the adhesive is applied to the bearing 11, it needs to be
used at temperature equal to or less than the heat resistance
temperature of the grease of the bearing 11, and the room
temperature curing-type epoxy resin adhesive is more preferable.
Characteristics of the adhesive are often indicated by tension
shear, compression shear, tensile strength, and peel strength, but
the compression strength of the resin is important in the present
configuration. Usually, a manufacturer of an adhesive hardly
releases a value of the compressive strength. Typically, the
compressive strength is about four times higher than the shear
strength that indicates characteristics of cohesive failure.
Therefore, the shear strength can be used as an index for selecting
an adhesive.
[0098] As described above, the epoxy resin-based adhesive is filled
in the gap between the inner peripheral surface 50a of the outer
ring holding portion 50 and the outer peripheral surface 23c of the
outer ring 23, and the gap between the outer peripheral surface 30a
of the inner ring holding portion 30 and the inner peripheral
surface 21c of the inner ring 21, so that the gaps are sealed.
Accordingly, even if a moment load is applied to the DD motor 10B,
the movement of the bearing 11 and the housing 7 (the housing inner
3 and the rotor flange 5) in the radial direction can be prevented.
Therefore, the DD motor 10B that sufficiently satisfies the
mechanical rigidity of the bearing 11 as well as the highly
accurate rotation of the DD motor 10B can be realized, and
erroneous detection in the resolver 27 can be prevented.
[0099] Furthermore, even if roundness error, surface roughness, and
dimension error occur in the inner peripheral surface 50a and the
outer peripheral surface 30a of the housing 7 (the housing inner 3
and the rotor flange 5) that supports the bearing 11, the rotation
center of the bearing 11 and the axial center of the housing 7 (the
housing inner 3 and the rotor flange 5) can be aligned by the
aligning action that occurs when the adhesive is filled in the
gaps.
[0100] In the third embodiment, the adhesives are respectively
filled in the gap between the inner peripheral surface 50a of the
outer ring holding portion 50 (rotor flange 5) and the outer
peripheral surface 23c of the outer ring 23 (bearing 11), and the
gap between the outer peripheral surface 30a of the inner ring
holding portion 30 (housing inner 3) and the inner peripheral
surface 21c of the inner ring 21 (bearing 11), whereby the movement
of the bearing 11 and the housing 7 (the housing inner 3 and the
rotor flange 5) in the radial direction is prevented, and the
aligning action of the bearing 11 and the housing 7 works.
Therefore, the process can be simplified in the machining process
of manufacturing the outer peripheral surface 30a of the inner ring
holding portion 30 (housing inner 3) and the inner peripheral
surface 50a of the outer ring holding portion 50 (rotor flange 5),
and the highly accurate DD motor 10B can be realized in an easier
and simpler manner with less cost.
[0101] Furthermore, even in a case where the above machining
process is simplified, by filling the adhesives in the gap between
the inner peripheral surface 50a of the outer ring holding portion
50 (rotor flange 5) and the outer peripheral surface 23c of the
outer ring 23 (bearing 11), and the gap between the outer
peripheral surface 30a of the inner ring holding portion 30
(housing inner 3) and the inner peripheral surface 21c of the inner
ring 21 (bearing 11), the following functions and effects are
exhibited. (A) Non-uniform metal contact between the inner ring 21
and the outer ring 23 of the bearing 11, and between the housing
inner 3 and the rotor flange 5 can be avoided. (B) Non-uniform and
excessive insertion such that the rolling element bearing ring of
the bearing 11 is distorted can be prevented. (C) The bearing 11
can be supported not to be shifted in the radial direction even if
a radial load is applied to the DD motor 10B from the outside. (D)
Tensile load or load in a peeling direction, other than the
compressive load that is applied non-uniformly on the entire
periphery, is not applied to the C-type retaining ring 53 and the
push ring 55, when a moment load is applied to the DD motor
10B.
Fourth Embodiment
[0102] FIG. 9 is a cross-sectional view illustrating a
configuration of a direct drive motor according to a fourth
embodiment. In the fourth embodiment, different portions from the
first embodiment will be described to avoid overlapping
description, and portions having similar configurations to the
first embodiment are denoted with the same reference signs and
description thereof is omitted. Furthermore, the configurations of
the second and third embodiments described above may be combined
with the fourth embodiment.
[0103] In a DD motor 10C according to the fourth embodiment, a
single resolver 27 as an incremental resolver that detects relative
displacement of a rotor 15 with respect to a stator 13 is arranged
in a housing 7 to suppress an increase in dimension in an axial
direction, similarly to the DD motor 10 according to the first
embodiment. The resolver 27 includes an annular resolver rotor 33
and a resolver stator 35 arranged to face the resolver rotor 33
with a predetermined interval. As described above, the resolver
rotor 33 is integrally attached to a resolver rotor fixing portion
5a formed on an inner peripheral surface of a rotor flange 5 with a
bolt 33a. Furthermore, the resolver stator 35 is integrally
attached to a resolver stator fixing portion 29a formed on an outer
peripheral surface of an inner ring holder 29 with a bolt 35a.
[0104] Typically, a resolver detects a rotation position according
to change of self-reactance, and is susceptible to surrounding
structures. Therefore, for example, in a configuration in which the
housing is arranged in proximity to an outer diameter side of the
resolver, a detection signal of the resolver is not stabilized, and
detection of a highly accurate rotational state may become
difficult.
[0105] Therefore, in the fourth embodiment, as illustrated in FIG.
9, a relief groove 5b for providing a space C is formed in the
resolver rotor fixing portion 5a of the rotor flange 5 at a facing
surface side facing the resolver rotor 33 fixed to the resolver
rotor fixing portion 5a (at an outer diameter surface side of the
resolver rotor 33 in FIG. 1). The relief groove 5b widens a
distance between an inner peripheral surface 5a1 of the resolver
rotor fixing portion 5a and an outside surface 33b in the radial
direction of the resolver rotor 33 facing the inner peripheral
surface 5a1. The relief groove 5b is provided throughout the entire
periphery of the inner peripheral surface 5a1 of the resolver rotor
fixing portion 5a so as to have a diameter increasing outward in
the radial direction. As described above, the resolver rotor 33 is
fixed to the rotor flange 5 to have the space C between the surface
33b at an opposite side to the facing surface facing the resolver
stator 35, and the inner peripheral surface 5a1 of the resolver
rotor fixing portion 5a.
[0106] In this configuration, the relief groove 5b is provided
throughout the entire periphery of the inner peripheral surface 5a1
of the resolver rotor fixing portion 5a, so that the space C can be
provided between the inner peripheral surface 5a1 and the outside
surface 33b in the radial direction of the resolver rotor 33.
Therefore, the space C allows the resolver 27 to be less
susceptible to an external magnetic flux, and can accurately detect
the reluctance change. Therefore, the rotational state of the DD
motor 10C can be accurately detected.
[0107] FIG. 10 is a schematic configuration diagram of an
inspection device 100 using the DD motor 10 (10A, 10B, or 10C) of
the above-described embodiments. A disk-like table 80 is coupled to
an upper end of the rotor flange 5 of the DD motor 10, and the
table 80 is rotated by an operation of the rotor flange 5.
Inspection target objects (objects to be conveyed or target
objects) 81 are arranged on an edge portion of the table 80 at
equal intervals. In this configuration, the inspection object 81 is
conveyed by being rotated together with the table 80 by an
operation of the DD motor 10, and a conveying device is configured
to have the DD motor 10 and the table 80. Furthermore, a camera
(inspection unit) 82 that individually observes the inspection
target objects 81 rotated (conveyed) together with the table 80 is
arranged above the edge portion of the table 80. Then, by capturing
images with the camera 82, the inspection target objects 81 can be
inspected based on the captured images. According to this
configuration, positional accuracy in moving the inspection target
objects 81 below the camera 82 can be enhanced, and a decrease in
size of the inspection device 100 can be realized.
[0108] FIG. 11 is a schematic configuration diagram of a machine
tool 101 using the DD motor 10 (10A, 10B, or 10C) of the
above-described embodiments. A disk-like table 80 is coupled to an
upper end of the rotor flange 5 of the DD motor 10, and the table
80 is rotated by an operation of the rotor flange 5. Machining
target objects (target objects) 91 are arranged on an edge portion
of the table 80 at equal intervals. Furthermore, a loading robot
(machining unit) that performs an operation to load new parts 92
and 93 on the machining target objects 91 is arranged at the edge
portion of the table 80, and can perform machining on the machining
target objects 91 in accordance with the rotation of the table 80.
According to this configuration, positional accuracy in moving the
machining target objects 91 to the position of the loading robot
can be enhanced, and a decrease in size of the machine tool 101 can
be realized.
[0109] As described above, according to the above-described
embodiments, the DD motor 10 includes: the bearing 11 including the
inner ring 21 and the outer ring 23 arranged to face each other
with the rolling element 25 interposed therebetween; and the
housing 7 including the housing inner 3 supported by the inner ring
21 and the rotor flange 5 supported by the outer ring 23. The rotor
flange 5 includes the flange portion 51 extending to the one end
surface 23a side in the axial direction of the outer ring 23, and
the C-type retaining ring 53 arranged at the other end surface 23b
side in the axial direction of the outer ring 23. The push ring 55
formed of a resin material is provided in the gap between the
flange portion 51 and the one end surface 23a in the axial
direction. Therefore, with the simple configuration, the width
dimensional tolerance of the bearing 11 in the axial direction can
be absorbed, and the movement of the bearing 11 in the axial
direction can be completely prevented.
[0110] Furthermore, according to the above-described embodiments,
the rotor flange 5 where the flange portion 51 is formed includes
the groove portion 52 extending in the circumferential direction,
and the C-type-retaining ring 53 is mounted in the groove portion
52. Therefore, the C-type retaining ring 53 can be easily attached,
and simplification of the support structure of the bearing 11 can
be realized.
[0111] Furthermore, according to the above-described embodiments,
the housing inner 3 and the rotor flange 5 are each formed into the
cylindrical shape, and the rotor flange 5 where the flange portion
51 is formed is seamlessly molded in an extending direction of the
cylinder. Therefore, the bearing 11 can be supported while an
increase in size of the rotor flange 5 in the axial direction can
be suppressed, and a decrease in size of the DD motor 10 can be
achieved.
[0112] Furthermore, according to the above-described embodiments,
the push ring 55 includes the first contact surface 55a being in
contact with the support surface 51a of the flange portion 51, and
the second contact surface 55b being in contact with the one end
surface 23a in the axial direction of the outer ring 23, and the
first contact surface 55a and the second contact surface 55b are
formed at positions shifted in the radial direction of the push
ring 55. Therefore, when a load is applied to the push ring 55, the
push ring 55 is distorted using the gap between the push ring 55
and the support surface 51a of the flange portion 51 or between the
push ring 55 and the one end surface 23a in the axial direction of
the outer ring 23. Therefore, a large distortion amount (deflection
amount) of the push ring 55 can be secured, which allows the push
ring 55 to be effectively deformed.
[0113] Furthermore, according to the above-described embodiments,
the DD motor 10 includes: the motor unit 9 including the stator 13
fixed to the housing inner 3, and the rotor 15 fixed to the rotor
flange 5 and rotatable with respect to the stator 13; and the
resolver 27 for detecting the rotational state of the motor unit 9.
The resolver 27 is a single resolver of an incremental type, which
detects the relative displacement of the rotor 15 with respect to
the stator 13. Therefore, an increase in height of the housing 7 in
the axial direction can be suppressed, and a decrease in size of
the DD motor 10 can be achieved.
[0114] Furthermore, according to the above-described embodiments,
the DD motor 10 includes: the power factor detection unit 41 that
detects a position where the power factor becomes 0 when power is
supplied to the motor unit 9; and the translocation control unit 43
that controls translocation of the motor unit 9 according to the
position where the power factor becomes 0 and the resolver signal
output from the resolver 27. Therefore, the absolute resolver is
unnecessary in detecting translocation timing of the motor current.
Therefore, it is not necessary to mount the two types of rotation
detectors including the absolute resolver and the incremental
resolver, unlike the conventional configuration, and the single
resolver configuration can be employed. Therefore, the rotational
state of the motor unit 9 can be accurately detected, and the
height of the DD motor 10 in the axial direction can be
suppressed.
[0115] Furthermore, according to the above-described embodiments,
the relief groove 5b for providing the space C is formed in the
resolver rotor fixing portion 5a of the rotor flange 5 at the
facing surface side facing the resolver rotor 33 fixed to the
resolver rotor fixing portion 5a (the outer diameter surface side
of the resolver rotor 33 in FIG. 1). Therefore, the resolver 27
becomes less susceptible to the external magnetic flux, and the
reluctance change can be accurately detected.
[0116] Furthermore, according to the above-described embodiments,
the motor unit 9, the bearing 11, and the resolver 27 are arranged
side by side in the axial direction of the bearing 11. Therefore,
it is possible to suppress an increase in size in the radial
direction about the rotation axis S, which allows the installation
area (so-called footprint) of the DD motor 10 to be reduced.
[0117] Furthermore, according to the above-described embodiments,
the push ring 55 is provided in the gap between the flange portion
51 and the one end surface 23a in the axial direction of the
bearing 11, and the first gap sealing members 65 are arranged in
the gap between the C-type retaining ring 53 and the other end
surface 23b in the axial direction of the bearing 11 and the gap
between the C-type retaining ring 53 and the groove portion 52.
Therefore, the first gap sealing members 65 seal the gap caused by
the waviness or the warp of the C-type retaining ring 53 or the
groove portion 52, whereby a decrease in rigidity of the DD motor
10A can be suppressed.
[0118] Furthermore, according to the above-described embodiments,
the first gap sealing member 65 is a resin film sticking on the
C-type retaining ring 53. Therefore, the first gap sealing members
65 can be easily arranged in the gap between the C-type retaining
ring 53 and the other end surface 23b in the axial direction of the
bearing 11 and the gap between the C-type retaining ring 53 and the
groove portion 52.
[0119] Furthermore, according to the above-described embodiments,
the first gap sealing member 65 is an adhesive including the main
agent, and the curing agent that is mixed with the main agent and
cures the main agent. Therefore, the adhesive is cured after the
C-type retaining ring 53 is mounted in the groove portion 52, so
that the gap caused by the waviness or the warp of the C-type
retaining ring 53 or the groove portion 52 can be easily
sealed.
[0120] Furthermore, according to the above-described embodiments,
the C-type retaining ring 53 is mounted in the groove portion 52 in
a state where one of the main agent and the curing agent is applied
on the other end surface 23b in the axial direction and the groove
portion 52 of the bearing 11, and the other of the main agent and
the curing agent is applied on the C-type retaining ring 53.
Therefore, premixture of the adhesive becomes unnecessary, and the
other end surface 23b in the axial direction and the groove portion
52 of the bearing 11 can be left in the state of the main agent or
the curing agent being applied, which improves flexibility in the
assembling process of the bearing 11.
[0121] Furthermore, according to the above-described embodiments,
the adhesive is configured such that the curing agent encapsulated
in microcapsules is mixed in the main agent, and when the
microcapsules are broken by external force, the curing agent and
the main agent are mixed and cured. Therefore, for example, the
adhesive is applied on the C-type retaining ring 53 in advance, so
that the adhesive can be cured after the C-type retaining ring 53
is mounted in the groove portion 52, and then it becomes easy to
handle the adhesive.
[0122] Furthermore, according to the above-described embodiments,
the second gap sealing member 66 is arranged in at least one of the
gap between the inner peripheral surface 21c of the inner ring 21
and the outer peripheral surface 30a of the inner ring holding
portion 30 (housing inner 3) and the gap between the outer
peripheral surface 23c of the outer ring 23 and the inner
peripheral surface 50a of the outer ring holding portion 50 (rotor
flange 5). Therefore, the second gap sealing member 66 seals the
gap, whereby simplification of machining of the housing 7 (the
housing inner 3 and the rotor flange 5) can be achieved, and the
movement of the bearing 11 in the radial direction can be
suppressed.
[0123] Furthermore, according to the above-described embodiments,
the second gap sealing member 66 is an adhesive that is cured after
being filled in the gap between the inner peripheral surface 21c of
the inner ring 21 and the outer peripheral surface 30a of the inner
ring holding portion 30 (housing inner 3) and the gap between the
outer peripheral surface 23c of the outer ring 23 and the inner
peripheral surface 50a of the outer ring holding portion 50 (rotor
flange 5). Therefore, alignment of the center of the bearing 11 and
the center of the housing 7 (the housing inner 3 and the rotor
flange 5) can be realized by balancing of tension by the adhesive
filled in the gaps.
[0124] Furthermore, according to the above-described embodiments,
the housing inner 3 and the rotor flange 5 are formed of a magnetic
body, and the electroless nickel-phosphorus plating process is
performed on the outer peripheral surface 30a of the inner ring
holding portion 30 (housing inner 3) and the inner peripheral
surface 50a of the outer ring holding portion 50 (rotor flange 5)
in which the second gap sealing member 66 is arranged. Therefore,
the aligning force can be increased, compared with one on which no
electroless nickel-phosphorus plating process is performed.
[0125] The embodiments have been described, but the embodiments are
not limited by the described content. In the above-described
embodiments, the DD motor 10 has been described as an example of
the bearing device. However, the embodiments are not limited to
motors as long as the support structure of the bearing described
above is included. Furthermore, the DD motor 10 of the present
embodiments is an outer rotor-type motor, but obviously, an inner
rotor-type motor is also employable. Furthermore, in the
above-described embodiments, the support structure of the bearing
11 is provided at the rotor flange 5 side. However, the embodiments
are not limited thereto, and the support structure may be provided
at the housing inner 3 side or at both sides. Furthermore, the push
ring 55 is most preferably installed between the flange portion 51
and the one end surface 23a in the axial direction of the bearing
11 (outer ring 23). However, the push ring 55 may be installed
between the C-type retaining ring 53 and the other end surface 23b
in the axial direction of the bearing 11 (outer ring 23).
Furthermore, the push rings 55 may be respectively installed at
both the end surface sides (the flange portion 51 side and the
C-type retaining ring 53 side) in the axial direction of the
bearing 11 (outer ring 23) depending on the characteristics of the
polymeric material. Furthermore, in the present embodiments, the
configuration including the single bearing 11 has been described.
However, similar effects can be obtained by a configuration in
which a plurality of bearings is combined and used (including a
case where a spacer is provided between the bearings). Furthermore,
in the above-described embodiments, the configuration in which the
inner ring 21 of the bearing 11 is sandwiched by the housing inner
3 and the inner ring holder 29 is employed. However, because the
outer ring 23 is firmly supported in the axial direction, the
housing inner 3 may be extended to the upper end as is the rotor
flange 5 so that the inner ring 21 can be fixed to the outer
peripheral surface of the housing inner 3 with an adhesive or by
means of shrinkage fitting.
REFERENCE SIGNS LIST
[0126] 3 HOUSING INNER (FIRST HOUSING) [0127] 5 ROTOR FLANGE
(SECOND HOUSING) [0128] 5a RESOLVER ROTOR FIXING PORTION [0129] 5b
RELIEF GROOVE [0130] 7 HOUSING [0131] 9 MOTOR UNIT [0132] 10, 10A,
10B, and 10C DD MOTOR (BEARING DEVICE) [0133] 11 BEARING [0134] 13
STATOR (STATIONARY ELEMENT) [0135] 15 ROTOR (ROTATING ELEMENT)
[0136] 20 CONTROL UNIT [0137] 21 INNER RING [0138] 21c INNER
PERIPHERAL SURFACE OF INNER RING [0139] 23 OUTER RING [0140] 23a
ONE END SURFACE IN AXIAL DIRECTION (ONE AXIAL-DIRECTION END
SURFACE) [0141] 23b THE OTHER END SURFACE IN AXIAL DIRECTION (THE
OTHER AXIAL-DIRECTION END SURFACE) [0142] 23c OUTER PERIPHERAL
SURFACE OF OUTER RING [0143] 25 ROLLING ELEMENT [0144] 27 RESOLVER
(ROTATION DETECTOR) [0145] 33 RESOLVER ROTOR [0146] 41 POWER FACTOR
DETECTION UNIT [0147] 43 TRANSLOCATION CONTROL UNIT [0148] 51
FLANGE PORTION [0149] 52 GROOVE PORTION [0150] 53 C-TYPE RETAINING
RING (RETAINING RING) [0151] 55, 155, and 255 PUSH RING [0152] 55a
and 155a FIRST CONTACT SURFACE [0153] 55b, 155b, and 155c SECOND
CONTACT SURFACE [0154] 55c FIRST INCLINED SURFACE [0155] 55d SECOND
INCLINED SURFACE [0156] 65 FIRST GAP SEALING MEMBER [0157] 66
SECOND GAP SEALING MEMBER [0158] 67 FILM [0159] 80 TABLE [0160] 81
INSPECTION TARGET OBJECT (OBJECT TO BE CONVEYED, TARGET OBJECT)
[0161] 82 CAMERA (INSPECTION UNIT) [0162] 91 MACHINING TARGET
OBJECT (TARGET OBJECT) [0163] 100 INSPECTION DEVICE [0164] 101
MACHINE TOOL [0165] C SPACE [0166] S ROTATION AXIS
* * * * *